The extension was granted because April 15 falls on a Sunday this year, and Monday is Emancipation Day, a holiday in Washington D.C. that celebrates the freeing of slaves in the district. Last year, Tax Day was extended until April 18, also thanks to Emancipation Day.

The IRS will also begin accepting returns submitted online through the agency's e-filing system -- which the IRS says is the fastest, most accurate filing option for taxpayers -- on January 17.